Glass-fiber reinforced composite pp-r pipe The pipe has three layer structure, the intermediate layer is the composite material for incresing rigidity and strength.This new kind of pipe inherites hot melt connectionáof the ordinary pp-r, having characteristics of three-high and one-low as high strength, toughness, rigidity and low linear expansion coefficient, remedying the application limitation of ordinary PP-R pipe in the vertical, outer and hot water pipe.